The invention relates to methods and apparatus for determining the thickness of a shim or shims required for positioning a ball joint in a suspension assembly of the vehicle. More particularly, the invention relates to such methods and apparatus to determine the as-built shim thickness.
In the past, persons making repairs in the field or in the manufacturing of suspension assemblies for vehicles, attempting to determine the required thickness of a shim for positioning or loading of the ball joint assembly usually required the complete assembly of the vehicle suspension assembly with a shim in place and then determined whether the ball joint was properly supported. The shim prevents end play of the ball joint in the suspension assembly. If the shim did not have the proper thickness it was necessary to remove the ball joint, replace the shim with another shim, either thicker or thinner, and reassemble the suspension assembly. This process was repeated until the proper shim thickness was found. Obviously, this required a great deal of time and effort.
The determination of this shim thickness for a ball joint in the suspension assembly of a vehicle having independent suspension, is extremely difficult because of end-play in the ball joint. Measurements for ball joint wear have a small margin for error requiring precise installation and measuring. Typical accuracy is the in the neighborhood of 0.001 inch.
Thus, there is a need for an apparatus and a method for determining the thickness of a shim for proper positioning of a ball joint in a suspension assembly of a vehicle before the suspension assembly is mounted to the vehicle.
There is provided a shim measuring apparatus to determine the thickness of a shim, with the shim used with a ball joint including a snap-ring and a control arm having a bore and a notch. The measuring apparatus comprises an upper housing including a measuring device and a lower housing coupled to the upper housing. The lower housing is configured to receive the ball joint and snap-ring and to engage the notch in the bore. The distance between the upper housing and the lower housing, while a load is applied, is measured by the measuring device. Such distance between the upper housing and the lower housing represents the shim thickness. The shim thickness represents the as built thickness of the shim to be used with the ball joint and snap-ring in the control arm. One embodiment provides that the measuring device is a dial indicator. A further embodiment provides the lower housing includes a collet ring having a plurality of collet fingers and a handle ring including a bearing ring and a taper ring wherein the collet fingers are configured to releasably engage the notch in the bore of the control arm.
There is also provided a measuring apparatus to determine the thickness of a shim, with the shim used with a ball joint including a snap-ring in a control arm having a bore and a notch. The measuring apparatus comprises a first means for housing including a means for measuring and a second means for housing coupled to the first means for housing. The second means for housing is configured to receive the ball joint and the snap-ring and engage the notch in the bore. The distance between the first means for housing and the second means for housing, while a load is applied, is measured by the means for measuring. The distance measured represents the shim thickness. A further embodiment provides that the first means for housing reflects the sum of a plurality of planes defined by the ball joint and the measuring apparatus in the bore of the control arm and the second means for housing reflects an upper plane of the notch in the bore. A further embodiment provides the measuring apparatus wherein the second means for housing including a collet ring having a plurality of means for engaging and a means for turning including a bearing ring and a means for pushing, wherein the means for engaging is configured to releasably engage the notch.
There is also provided a method for determining the as-built thickness of a shim used with a ball joint and snap-ring in a control arm, with the control arm having a bore and a notch. The method includes using a measuring apparatus having an upper housing including a measuring device and a lower housing including a collet ring having plurality of collet fingers, a handle ring including a bearing ring retaining ball bearings, and a taper ring. The method comprises the steps of installing a lower housing in the bore of the control arm and installing the ball joint in the lower housing and placing the snap-ring on the ball joint. The ball joint is positioned 180xc2x0 from its usual working position. Then coupling the upper housing to the lower housing and applying an external, axial force to the measuring apparatus. Turning the handle ring in a counter-clock-wise direction, wherein the collet fingers engage an upper plane of the notch. Than reading the measuring device to obtain the distance between the upper housing and the lower housing, while under load, which represents the as-built shim thickness. Another embodiment includes a step of reading each measuring device which is at least two dial indicators and averaging the readings of all the dial indicators to obtain the shim thickness. Another embodiment includes the step of coupling a torque limiting assembly to the handle ring wherein the turning of the handle ring is limited to a torque sufficient to force the collet fingers up against the upper plane of the notch. The torque limiting assembly can provide a set screw for setting the torque limit by adjusting the set screw in the torque limiting assembly.